136 



NATURE 



[March 31, 192 1 



upon them as if he liked them. A special feature 

 is made of the treatment of the " laws of momen- 

 tum," which replace Newton's laws of motion. 

 This treatment is as follows : — After a cursory 

 refei:«nce to mass on p. 2, two chapters are devoted 

 to kinematics. In chap, iii., p. 57, momentum is 

 defined. Then the "first law " appears (p. 58) : — 



" In any body or system, the total momentum 

 remains constant unless the body or system is 

 acted upon by some external force. . . . 



"The first law introduces a new term, viz. 

 force, which may, for the present, be defined 

 thus : — 



" Force is that which produces or tends to pro- 

 duce a change of momentum. 



" The law is the result of observation." 



We prefer Newton, but it is only fair to recog- 

 nise that *' laws " are always a difficulty in ele- 

 mentary mechanics, and on the whole we are in- 

 clined to recommend the book. H. B. H. 



Our Bookshelf. 



Animal Life in South Africa. By S. H. Skaife. 

 With an introduction by Prof. F. Clarke. 

 Pp. X + 281. (Cape Town: T. Maskew^ Miller; 

 Oxford : Basil Blackwell, 1920.) 155. net. 



This book is intended to help teachers and pupils 

 in South Africa to get to know some of the 

 common animals of every grade. It is clearly 

 written and abundantly illustrated with simple 

 " thumbnail " sketches, many of which will enable 

 the student to identify what he has seen. More 

 critical sifting of the illustrations would have 

 eliminated a number — e.g. that of Apus — which 

 blur the total impression. It is almost impossible, 

 except for men like Huxley, gifted with an unusual 

 educational sense, to write a book useful for 

 teachers and pupils alike, and though Mr. Skaife 

 has done well, he sometimes falls between two 

 stools — being sometimes too simple, sometimes a 

 little difficult. There are also various statements 

 requiring reconsideration, we think ; thus we do 

 not believe that the liver-fluke feeds partly on 

 bile, and we are sure that a sea-urchin's teeth do 

 not work up and down in their sheaths. But 

 these are small matters ; we mention them only 

 as instances of a kind of defect that might easily 

 be remedied, for the book as a whole is sound 

 and careful, and it will be of great service. The 

 chapters on insects, spiders, scorpions, and ticks 

 are particularly good. We are interested to read 

 that Peripatus may be fed on raw minced liver. 

 "A female with twenty to thirty young ones 

 clustering around her like chicks round a hen 

 make a very pretty family party." Two educa- 

 tional remarks seem called for: (i) It is very 

 doubtful whether we are warranted in using a 

 word like " ugly " for such animals as the fishing- 

 frog or Galeodes — it seems like undoing one of 

 NO. 2683, VOL. 107] 



the endeavour^ of Nature-study, which is to show 

 that no wholesome free-living wild creature can 

 be called common or unclean. (2) Is there not 

 more than once— e.^. in regard to flat worms and 

 gapes-worms — a distinct and deplorable tendency 

 to bowdlerise the elementary facts of sex? Be- 

 cause we appreciate Mr. Skaife's good workman- 

 ship, we would ask him to reconsider these points. 

 The book appears to be extraordinarily dear. 



Anniversaries and Other Poems. By Leonard 

 Huxley. Pp. x4-82. (London: John Murray, 

 1920.) 55. net. 



A BOOK of dignified and melodious poems, in 

 which it is interesting to observe the natural 

 history touches — the child's poetic vision is com- 

 pared to that of some under-water larval creature, 

 glimpsing the sky, seeing "crooked tops to the tall, 

 straight trees " ; the full waves of the floral tide 

 in a southern April, breaking on the hill "with 

 white narcissus for their foam," are contrasted 

 with the shyer coming in the north, with "less 

 of fire and more of dew," and yet with its own 

 exuberance, for 



bluebells thick in budding woods 

 Stretch pool on pool from tree to tree, 

 All heaven in their dew-drenched floods 

 Of blue that mock your Midland sea. 



Mr. Leonard Huxley is a lover of Nature, both 

 of the great appeals and of the tiniest things 

 that pass from sense to soul, from Nature's heart 

 to man's. Common things are dear to him in 

 themselves, not merely as emblems. Of the speed- 

 well, "blue flower of happy name," he writes: — 



It buds on every fallow swell, 



And the bright wish it bids me frame 



Fills earth as ipusic fills a shell. 



. Nature may or may not be fathomable, but 

 surely it is still unfathomed, and we are among 

 the heretics who think that of some of its depths 

 not reached by the scientific dredge we get an 

 inkling by the medium of disciplined feeling. Mr. 

 Huxley makes his contribution, a perfectly clear- 

 eyed one, and we do not agree more than a very 

 little with the mood of the last poem, "The Land 

 of Might-Have-Been," "portioned with felicity" 

 though that mood be. The author has gone much 

 further than that. 



Mechanism, Life, and Personality : An Examina- 

 tion of the Mechanistic Theory of Life and 

 Mind. By Dr. J. S. Haldane. Second edition. 

 Pp. vii+152. (London: Johh Murray, 1921.) 

 6s. net. 

 The new edition of Dr. Haldane 's little work is 

 substantially the same, so far as subject-matter 

 is concerned, as the first edition, which was re- 

 viewed in Nature for October 22, 1914. It is in 

 the fourth lecture, on personality, that the main 

 changes have been made. The whole chapter has 

 been recast, and some additional matter inserted 

 with the object of bringing home to the reader 

 more certainlv the meaning of this admittedly 

 difficult subject. 



